Gatherings of more than six people are banned in England.
Abraham was thrown a surprise birthday party after turning 23 on Saturday, with Borussia Dortmund talisman Sancho also in attendance at the Chelsea forward's mansion in London.
Sancho released a statement yesterday, saying: 'I would like to apologise for breaking the guidelines and although I was unaware upon arriving of the numbers attending, I take full responsibility for my actions.
The England manager had already planned to remind all his players of their responsibilities at a team meeting on Monday night after he was forced to axe Harry Maguire from his squad following allegations of a violent altercation with Greek police before booting youngsters Mason Greenwood and Phil Foden out his squad after the pair invited two girls back to the team hotel following the win over Iceland.
"All I can do now is learn from it, apologize to everyone and ensure it never happens again".
The FA says the delay is a precaution while it assesses if there is any risk to the wider group.
Newspaper reports from the weekend showed a party in his house at that time.
The forward sustained the problem during Manchester City's 1-1 draw with Leeds on Saturday, a game in which he scored.
The party could provide yet another headache for Three Lions boss Gareth Southgate, who will be preparing his side to take on Wales in a friendly on Thursday before UEFA Nations League clashes with Belgium and Denmark on Sunday and Wednesday, respectively.
"Separately, Raheem Sterling has actually been eliminated of all 3 components through injury".
Chelsea defender Reece James has earned his maiden call-up to the squad, having earned a promotion from the under-21s.